Our ship will dock at 8 am at Civitavecchia on a Tuesday. I have already purchased the Vitican museum tour that starts at 10:30 am. Now I am worried about whether I'll be able to arrive on time at the Vatican museum.

I am planning to do the following:
Take the train from Civ to Stazion St Roma S. Pietro, then take a taxi to the Vatican museum.
Is it hard to find a taxi around 10 am on a Tuesday morning that will take us to the Vatican museum ? How long will it take the taxi to get there (still rush hour travel at that time)?

Other than the above, is there any easier and faster way to get to the Vatican museum by 10:30 am. I understand it is quite far to walk.